Most astronomical "science" is purely theoretical mind you. For all of what we really know the sun could transform into a giant basketball instead of doing all that stuff.
And we're more than ready for any asteroid. Theres an effective counter-asteroid procedure demonstrated with cutting edge late 90s special effects in the movie "armageddon" lol.
We know all about the suns fate due to gazing at stars which have already gone supernova. That one's a given. Whoever's living on this planet when it starts can do nothing about that one.
History also tells us that an asteroid strike is a certainty, but, unlike the sun scenario where we have to wait a couple of billion years before it all starts, the asteroid could hit us even within our lifetime, or not, their's no given with that one.
And the science fiction approach to an asteroid isn't beyond the realms of possibility. Knocking it off course to alter its trajectory years before it even gets near us is doable, sort of, but not currently.
It needs trillions and trillions of $ throwing at research and execution, and we're not even close. Instead of the world combining their efforts, and money, into a global strategy against an asteroid hit, those trillions and trillions are currently going on each others self defence to protect us from one another!! It's laughable really and just shows you what a stupid race of creatures we really are, lol.